Agent overused smart_edit (whole-file LLM call, weak context). Rewrite the
FilesystemTool description decision tree so edit (exact text) is the default and
edit_lines (by line numbers) is the deterministic option; smart_edit is reserved
for genuinely semantic changes that cannot be expressed as exact text or line
numbers. Strengthen the old_not_unique hint to steer back to edit/edit_lines
before smart_edit. Add an "Editing policy" section to the navi_code and
developer profile prompts reinforcing the same priority.

Co-Authored-By: Claude <noreply@anthropic.com>